#include <cnix/compiler.h>
#include <cnix/fs.h>
#include "ext2.h"

#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)

extern struct ext2_group_desc * ext2_get_group_desc(struct ext2_sb_info * sbi,
               unsigned int block_group,
               struct buf_head ** bh);

/**
 * ext2_init_block_alloc_info()
 * @inode:    file inode structure
 *
 * Allocate and initialize the  reservation window structure, and
 * link the window to the ext2 inode structure at last
 *
 * The reservation window structure is only dynamically allocated
 * and linked to ext2 inode the first time the open file
 * needs a new block. So, before every ext2_new_block(s) call, for
 * regular files, we should check whether the reservation window
 * structure exists or not. In the latter case, this function is called.
 * Fail to do so will result in block reservation being turned off for that
 * open file.
 *
 * This function is called from ext2_get_blocks_handle(), also called
 * when setting the reservation window size through ioctl before the file
 * is open for write (needs block allocation).
 *
 * Needs truncate_mutex protection prior to calling this function.
 */
void ext2_init_block_alloc_info(struct inode *inode)
{
  struct ext2_inode_info *ei = EXT2_I(inode);
  struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
  struct super_block *sb = inode->i_sb;

  block_i = (struct ext2_block_alloc_info *)
						kmalloc(sizeof(*block_i), PageWait);
	if(!block_i){
		printk("kmalloc failed. %s %s\n",__func__,__FILE__);
		BUG();
	}

  struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node;

  rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
  rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;

  /*
   * if filesystem is mounted with NORESERVATION, the goal
   * reservation window size is set to zero to indicate
   * block reservation is off
   */
  if (!test_opt(sb, RESERVATION)){
		printk("I think we can support reservation for CNIX. %s %s\n",
			__func__,__FILE__);
		BUG();
    rsv->rsv_goal_size = 0;
  }else
    rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS;
  rsv->rsv_alloc_hit = 0;
  block_i->last_alloc_logical_block = 0;
  block_i->last_alloc_physical_block = 0;
  ei->i_block_alloc_info = block_i;
}

/**
 * ext2_has_free_blocks()
 * @sbi:    in-core super block structure.
 *
 * Check if filesystem has at least 1 free block available for allocation.
 */
static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
{
  ext2_fsblk_t free_blocks, root_blocks;

  free_blocks = sbi->s_freeblocks_counter;
  root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);

	/*
	 *These advanced checks are a little bit far from my life.
	 *I therefore ignore it for now.
	 *Feel free to add this if needed.
	 */
  if (free_blocks < root_blocks + 1/* && !capable(CAP_SYS_RESOURCE) &&
    sbi->s_resuid != current_fsuid() &&
    (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))*/) {
		//printk("free_blocks: %u root_blocks: %u\n",(unsigned)free_blocks,(unsigned)root_blocks);
    return 0;
  }
  return 1;
}

/*
 * rsv_is_empty() -- Check if the reservation window is allocated.
 * @rsv:    given reservation window to check
 *
 * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED.
 */
static inline int rsv_is_empty(struct ext2_reserve_window *rsv)
{
  /* a valid reservation end block could not be 0 */
  return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED);
}

#if 0
//Let's just keep this for now, in case we may need them to do some debugging later.
extern unsigned long generic_find_next_zero_le_bit(const unsigned long *addr, unsigned
    long size, unsigned long offset);
int ext2_find_next_zero_bit1(u8_t *addr,int size,int off)
{
	int i;
	printk("size: %d off: %d\n",size,off);
	printk("%x %x %x %x\n",*((unsigned*)addr),*(((unsigned*)addr)+1),*(((unsigned*)addr)+2),*(((unsigned*)addr)+3));
	for(i=off;i<size;i++){
		int q = i>>3;
		int r = i&0x7;

		if(!((*(addr+q)) & (1<<r))){
			printk("%x %d\n",(unsigned)(*(addr+q)),r);
			break;
		}
	}
	printk("found it: %d\n",i);
	return i;
}
#endif

extern unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
         unsigned long offset);
static int ext2_valid_block_bitmap(struct super_block *sb,
          struct ext2_group_desc *desc,
          unsigned int block_group,
          struct buf_head *bh)
{
  ext2_grpblk_t offset;
  ext2_grpblk_t next_zero_bit;
  ext2_fsblk_t bitmap_blk;
  ext2_fsblk_t group_first_block;

  group_first_block = ext2_group_first_block_no(EXT2_SB(sb), block_group);

  /* check whether block bitmap block number is set */
  bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);

  offset = bitmap_blk - group_first_block;
  if (!ext2_test_bit(offset, bh->b_data))
    /* bad block bitmap */
    goto err_out;

  /* check whether the inode bitmap block number is set */
  bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
  offset = bitmap_blk - group_first_block;
  if (!ext2_test_bit(offset, bh->b_data))
    /* bad block bitmap */
    goto err_out;

  /* check whether the inode table block number is set */
  bitmap_blk = le32_to_cpu(desc->bg_inode_table);
  offset = bitmap_blk - group_first_block;
  next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
        offset + EXT2_SB(sb)->s_itb_per_group,
        offset);
  if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
    /* good bitmap for inode tables */
    return 1;

err_out:
  printk("Invalid block bitmap block_group = %d, block = %u\n",
      block_group, bitmap_blk);
  return 0;
}

/*
 * Read the bitmap for a given block_group,and validate the
 * bits for block/inode/inode tables are set in the bitmaps
 *
 * Return buffer_head on success or NULL in case of failure.
 */
static struct buf_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
  struct ext2_group_desc * desc;
  struct buf_head * bh = NULL;
  ext2_fsblk_t bitmap_blk;

  desc = ext2_get_group_desc(EXT2_SB(sb), block_group, NULL);
  if (!desc){
		printk("failed to get ext2 group descriptor. %s %s\n",
			__func__,__FILE__);
		BUG();
	}
  bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
  bh = sd_bread(sb->s_dev, bitmap_blk*EXT2_BLOCK_GRAN);
  if (unlikely(!bh)) {
    printk(__func__,
          "Cannot read block bitmap - "
          "block_group = %d, block_bitmap = %u",
          block_group, le32_to_cpu(desc->bg_block_bitmap));
		BUG();
  }
  if(!ext2_valid_block_bitmap(sb, desc, block_group, bh)){
		printk("invalid ext2 block bitmap. %s %s\n",
			__func__,__FILE__);
		BUG();
	}
  /*
   * file system mounted not to panic on error, continue with corrupt
   * bitmap
   */
  return bh;
}

static void group_adjust_blocks(struct super_block *sb, int group_no,
  struct ext2_group_desc *desc, struct buf_head *bh, int count)
{
  if (count) {
    unsigned free_blocks;

    free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
    desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
		bh->b_flags |= B_DIRTY;
  }
}

/**
 * goal_in_my_reservation()
 * @rsv:    inode's reservation window
 * @grp_goal:   given goal block relative to the allocation block group
 * @group:    the current allocation block group
 * @sb:     filesystem super block
 *
 * Test if the given goal block (group relative) is within the file's
 * own block reservation window range.
 *
 * If the reservation window is outside the goal allocation group, return 0;
 * grp_goal (given goal block) could be -1, which means no specific
 * goal block. In this case, always return 1.
 * If the goal block is within the reservation window, return 1;
 * otherwise, return 0;
 */
static int
goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal,
      unsigned int group, struct super_block * sb)
{
  ext2_fsblk_t group_first_block, group_last_block;

  group_first_block = ext2_group_first_block_no(EXT2_SB(sb), group);
  group_last_block = group_first_block + EXT2_BLOCKS_PER_GROUP(sb) - 1;

  if ((rsv->_rsv_start > group_last_block) ||
      (rsv->_rsv_end < group_first_block))
    return 0;
  if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
    || (grp_goal + group_first_block > rsv->_rsv_end)))
    return 0;
  return 1;
}

/*
 * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree.
 * @sb:     super block
 * @rsv:    reservation window to add
 *
 * Must be called with rsv_lock held.
 */
void ext2_rsv_window_add(struct super_block *sb,
        struct ext2_reserve_window_node *rsv)
{
  struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root;
  struct rb_node *node = &rsv->rsv_node;
  ext2_fsblk_t start = rsv->rsv_start;

  struct rb_node ** p = &root->rb_node;
  struct rb_node * parent = NULL;
  struct ext2_reserve_window_node *this;

  while (*p)
  {
    parent = *p;
    this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node);

    if (start < this->rsv_start)
      p = &(*p)->rb_left;
    else if (start > this->rsv_end)
      p = &(*p)->rb_right;
    else {
      //rsv_window_dump(root, 1);
			printk("rsv window error. %s %s\n",__func__,__FILE__);
      BUG();
    }
  }

  rb_link_node(node, parent, p);
  rb_insert_color(node, root);
}

/**
 * rsv_window_remove() -- unlink a window from the reservation rb tree
 * @sb:     super block
 * @rsv:    reservation window to remove
 *
 * Mark the block reservation window as not allocated, and unlink it
 * from the filesystem reservation window rb tree. Must be called with
 * rsv_lock held.
 */
static void rsv_window_remove(struct super_block *sb,
            struct ext2_reserve_window_node *rsv)
{
  rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
  rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
  rsv->rsv_alloc_hit = 0;
  rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root);
}

/**
 * search_reserve_window()
 * @rb_root:    root of reservation tree
 * @goal:   target allocation block
 *
 * Find the reserved window which includes the goal, or the previous one
 * if the goal is not in any window.
 * Returns NULL if there are no windows or if all windows start after the goal.
 */
static struct ext2_reserve_window_node *
search_reserve_window(struct rb_root *root, ext2_fsblk_t goal)
{
  struct rb_node *n = root->rb_node;
  struct ext2_reserve_window_node *rsv;

  if (!n)
    return NULL;

  do {
    rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);

    if (goal < rsv->rsv_start)
      n = n->rb_left;
    else if (goal > rsv->rsv_end)
      n = n->rb_right;
    else
      return rsv;
  } while (n);
  /*
   * We've fallen off the end of the tree: the goal wasn't inside
   * any particular node.  OK, the previous node must be to one
   * side of the interval containing the goal.  If it's the RHS,
   * we need to back up one.
   */
  if (rsv->rsv_start > goal) {
    n = rb_prev(&rsv->rsv_node);
    rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
  }
  return rsv;
}

/**
 * 	find_next_reservable_window():
 *		find a reservable space within the given range.
 *		It does not allocate the reservation window for now:
 *		alloc_new_reservation() will do the work later.
 *
 * 	@search_head: the head of the searching list;
 *		This is not necessarily the list head of the whole filesystem
 *
 *		We have both head and start_block to assist the search
 *		for the reservable space. The list starts from head,
 *		but we will shift to the place where start_block is,
 *		then start from there, when looking for a reservable space.
 *
 * 	@size: the target new reservation window size
 *
 * 	@group_first_block: the first block we consider to start
 *			the real search from
 *
 * 	@last_block:
 *		the maximum block number that our goal reservable space
 *		could start from. This is normally the last block in this
 *		group. The search will end when we found the start of next
 *		possible reservable space is out of this boundary.
 *		This could handle the cross boundary reservation window
 *		request.
 *
 * 	basically we search from the given range, rather than the whole
 * 	reservation double linked list, (start_block, last_block)
 * 	to find a free region that is of my size and has not
 * 	been reserved.
 *
 */
static int find_next_reservable_window(
				struct ext2_reserve_window_node *search_head,
				struct ext2_reserve_window_node *my_rsv,
				struct super_block * sb,
				ext2_fsblk_t start_block,
				ext2_fsblk_t last_block)
{
	struct rb_node *next;
	struct ext2_reserve_window_node *rsv, *prev;
	ext2_fsblk_t cur;
	int size = my_rsv->rsv_goal_size;

	/* TODO: make the start of the reservation window byte-aligned */
	/* cur = *start_block & ~7;*/
	cur = start_block;
	rsv = search_head;
	if (!rsv)
		return -1;

	while (1) {
		if (cur <= rsv->rsv_end)
			cur = rsv->rsv_end + 1;

		/* TODO?
		 * in the case we could not find a reservable space
		 * that is what is expected, during the re-search, we could
		 * remember what's the largest reservable space we could have
		 * and return that one.
		 *
		 * For now it will fail if we could not find the reservable
		 * space with expected-size (or more)...
		 */
		if (cur > last_block)
			return -1;		/* fail */

		prev = rsv;
		next = rb_next(&rsv->rsv_node);
		rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node);

		/*
		 * Reached the last reservation, we can just append to the
		 * previous one.
		 */
		if (!next)
			break;

		if (cur + size <= rsv->rsv_start) {
			/*
			 * Found a reserveable space big enough.  We could
			 * have a reservation across the group boundary here
		 	 */
			break;
		}
	}
	/*
	 * we come here either :
	 * when we reach the end of the whole list,
	 * and there is empty reservable space after last entry in the list.
	 * append it to the end of the list.
	 *
	 * or we found one reservable space in the middle of the list,
	 * return the reservation window that we could append to.
	 * succeed.
	 */

	if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
		rsv_window_remove(sb, my_rsv);

	/*
	 * Let's book the whole avaliable window for now.  We will check the
	 * disk bitmap later and then, if there are free blocks then we adjust
	 * the window size if it's larger than requested.
	 * Otherwise, we will remove this node from the tree next time
	 * call find_next_reservable_window.
	 */
	my_rsv->rsv_start = cur;
	my_rsv->rsv_end = cur + size - 1;
	my_rsv->rsv_alloc_hit = 0;

	if (prev != my_rsv)
		ext2_rsv_window_add(sb, my_rsv);

	return 0;
}

/**
 * bitmap_search_next_usable_block()
 * @start:    the starting block (group relative) of the search
 * @bh:     bufferhead contains the block group bitmap
 * @maxblocks:    the ending block (group relative) of the reservation
 *
 * The bitmap search --- search forward through the actual bitmap on disk until
 * we find a bit free.
 */
static ext2_grpblk_t
bitmap_search_next_usable_block(ext2_grpblk_t start, struct buf_head *bh,
          ext2_grpblk_t maxblocks)
{
  ext2_grpblk_t next;

  next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
  if (next >= maxblocks)
    return -1;
  return next;
}

/**
 * 	alloc_new_reservation()--allocate a new reservation window
 *
 *		To make a new reservation, we search part of the filesystem
 *		reservation list (the list that inside the group). We try to
 *		allocate a new reservation window near the allocation goal,
 *		or the beginning of the group, if there is no goal.
 *
 *		We first find a reservable space after the goal, then from
 *		there, we check the bitmap for the first free block after
 *		it. If there is no free block until the end of group, then the
 *		whole group is full, we failed. Otherwise, check if the free
 *		block is inside the expected reservable space, if so, we
 *		succeed.
 *		If the first free block is outside the reservable space, then
 *		start from the first free block, we search for next available
 *		space, and go on.
 *
 *	on succeed, a new reservation will be found and inserted into the list
 *	It contains at least one free block, and it does not overlap with other
 *	reservation windows.
 *
 *	failed: we failed to find a reservation window in this group
 *
 *	@rsv: the reservation
 *
 *	@grp_goal: The goal (group-relative).  It is where the search for a
 *		free reservable space should start from.
 *		if we have a goal(goal >0 ), then start from there,
 *		no goal(goal = -1), we start from the first block
 *		of the group.
 *
 *	@sb: the super block
 *	@group: the group we are trying to allocate in
 *	@bitmap_bh: the block group block bitmap
 *
 */
static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv,
		ext2_grpblk_t grp_goal, struct super_block *sb,
		unsigned int group, struct buf_head *bitmap_bh)
{
	struct ext2_reserve_window_node *search_head;
	ext2_fsblk_t group_first_block, group_end_block, start_block;
	ext2_grpblk_t first_free_block;
	struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root;
	unsigned long size;
	int ret;

	group_first_block = ext2_group_first_block_no(EXT2_SB(sb), group);
	group_end_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);

	if (grp_goal < 0)
		start_block = group_first_block;
	else
		start_block = grp_goal + group_first_block;

	size = my_rsv->rsv_goal_size;

	if (!rsv_is_empty(&my_rsv->rsv_window)) {
		/*
		 * if the old reservation is cross group boundary
		 * and if the goal is inside the old reservation window,
		 * we will come here when we just failed to allocate from
		 * the first part of the window. We still have another part
		 * that belongs to the next group. In this case, there is no
		 * point to discard our window and try to allocate a new one
		 * in this group(which will fail). we should
		 * keep the reservation window, just simply move on.
		 *
		 * Maybe we could shift the start block of the reservation
		 * window to the first block of next group.
		 */

		if ((my_rsv->rsv_start <= group_end_block) &&
				(my_rsv->rsv_end > group_end_block) &&
				(start_block >= my_rsv->rsv_start))
			return -1;

		if ((my_rsv->rsv_alloc_hit >
		     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
			/*
			 * if the previously allocation hit ratio is
			 * greater than 1/2, then we double the size of
			 * the reservation window the next time,
			 * otherwise we keep the same size window
			 */
			size = size * 2;
			if (size > EXT2_MAX_RESERVE_BLOCKS)
				size = EXT2_MAX_RESERVE_BLOCKS;
			my_rsv->rsv_goal_size= size;
		}
	}

	/*
	 * shift the search start to the window near the goal block
	 */
	search_head = search_reserve_window(fs_rsv_root, start_block);

	/*
	 * find_next_reservable_window() simply finds a reservable window
	 * inside the given range(start_block, group_end_block).
	 *
	 * To make sure the reservation window has a free bit inside it, we
	 * need to check the bitmap after we found a reservable window.
	 */
retry:
	ret = find_next_reservable_window(search_head, my_rsv, sb,
						start_block, group_end_block);

	if (ret == -1) {
		if (!rsv_is_empty(&my_rsv->rsv_window))
			rsv_window_remove(sb, my_rsv);
		return -1;
	}

	/*
	 * On success, find_next_reservable_window() returns the
	 * reservation window where there is a reservable space after it.
	 * Before we reserve this reservable space, we need
	 * to make sure there is at least a free block inside this region.
	 *
	 * Search the first free bit on the block bitmap.  Search starts from
	 * the start block of the reservable space we just found.
	 */
	first_free_block = bitmap_search_next_usable_block(
			my_rsv->rsv_start - group_first_block,
			bitmap_bh, group_end_block - group_first_block + 1);

	if (first_free_block < 0) {
		/*
		 * no free block left on the bitmap, no point
		 * to reserve the space. return failed.
		 */
		if (!rsv_is_empty(&my_rsv->rsv_window))
			rsv_window_remove(sb, my_rsv);
		return -1;		/* failed */
	}

	start_block = first_free_block + group_first_block;
	/*
	 * check if the first free block is within the
	 * free space we just reserved
	 */
	if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
		return 0;		/* success */
	/*
	 * if the first free bit we found is out of the reservable space
	 * continue search for next reservable space,
	 * start from where the free block is,
	 * we also shift the list head to where we stopped last time
	 */
	search_head = my_rsv;
	goto retry;
}

/**
 * try_to_extend_reservation()
 * @my_rsv:		given reservation window
 * @sb:			super block
 * @size:		the delta to extend
 *
 * Attempt to expand the reservation window large enough to have
 * required number of free blocks
 *
 * Since ext2_try_to_allocate() will always allocate blocks within
 * the reservation window range, if the window size is too small,
 * multiple blocks allocation has to stop at the end of the reservation
 * window. To make this more efficient, given the total number of
 * blocks needed and the current size of the window, we try to
 * expand the reservation window size if necessary on a best-effort
 * basis before ext2_new_blocks() tries to allocate blocks.
 */
static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv,
			struct super_block *sb, int size)
{
	struct ext2_reserve_window_node *next_rsv;
	struct rb_node *next;

	next = rb_next(&my_rsv->rsv_node);

	if (!next)
		my_rsv->rsv_end += size;
	else {
		next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node);

		if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
			my_rsv->rsv_end += size;
		else
			my_rsv->rsv_end = next_rsv->rsv_start - 1;
	}
}

/**
 * find_next_usable_block()
 * @start:    the starting block (group relative) to find next
 *      allocatable block in bitmap.
 * @bh:     bufferhead contains the block group bitmap
 * @maxblocks:    the ending block (group relative) for the search
 *
 * Find an allocatable block in a bitmap.  We perform the "most
 * appropriate allocation" algorithm of looking for a free block near
 * the initial goal; then for a free byte somewhere in the bitmap;
 * then for any free bit in the bitmap.
 */
static void *memscan(void *addr, int c, size_t size)
{
  if (!size)
    return addr;
  asm volatile("repnz; scasb\n\t"
      "jnz 1f\n\t"
      "dec %%edi\n"
      "1:"
      : "=D" (addr), "=c" (size)
      : "0" (addr), "1" (size), "a" (c)
      : "memory");
  return addr;
}

static ext2_grpblk_t
find_next_usable_block(int start, struct buf_head *bh, int maxblocks)
{
  ext2_grpblk_t here, next;
  char *p, *r;

  if (start > 0) { 
    /*   
     * The goal was occupied; search forward for a free 
     * block within the next XX blocks.
     *
     * end_goal is more or less random, but it has to be
     * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
     * next 64-bit boundary is simple..
     */
    ext2_grpblk_t end_goal = (start + 63) & ~63; 
    if (end_goal > maxblocks)
      end_goal = maxblocks;
    here = ext2_find_next_zero_bit(bh->b_data, end_goal, start);
    if (here < end_goal)
      return here;
    //printk("Bit not found near goal\n");
  }

  here = start;
  if (here < 0) 
    here = 0; 

  p = ((char *)bh->b_data) + (here >> 3);
  r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3)); 
  next = (r - ((char *)bh->b_data)) << 3;

  if (next < maxblocks && next >= here)
    return next;

  here = bitmap_search_next_usable_block(here, bh, maxblocks);
  return here;
}

/*
 * ext2_try_to_allocate()
 * @sb:			superblock
 * @handle:		handle to this transaction
 * @group:		given allocation block group
 * @bitmap_bh:		bufferhead holds the block bitmap
 * @grp_goal:		given target block within the group
 * @count:		target number of blocks to allocate
 * @my_rsv:		reservation window
 *
 * Attempt to allocate blocks within a give range. Set the range of allocation
 * first, then find the first free bit(s) from the bitmap (within the range),
 * and at last, allocate the blocks by claiming the found free bit as allocated.
 *
 * To set the range of this allocation:
 * 	if there is a reservation window, only try to allocate block(s)
 * 	from the file's own reservation window;
 * 	Otherwise, the allocation range starts from the give goal block,
 * 	ends at the block group's last block.
 *
 * If we failed to allocate the desired block then we may end up crossing to a
 * new bitmap.
 */
static int
ext2_try_to_allocate(struct super_block *sb, int group,
			struct buf_head *bitmap_bh, ext2_grpblk_t grp_goal,
			unsigned long *count,
			struct ext2_reserve_window *my_rsv)
{
	ext2_fsblk_t group_first_block;
       	ext2_grpblk_t start, end;
	unsigned long num = 0;

	/* we do allocation within the reservation window if we have a window */
	if (my_rsv) {
		group_first_block = ext2_group_first_block_no(EXT2_SB(sb), group);
		if (my_rsv->_rsv_start >= group_first_block)
			start = my_rsv->_rsv_start - group_first_block;
		else
			/* reservation window cross group boundary */
			start = 0;
		end = my_rsv->_rsv_end - group_first_block + 1;
		if (end > EXT2_BLOCKS_PER_GROUP(sb))
			/* reservation window crosses group boundary */
			end = EXT2_BLOCKS_PER_GROUP(sb);
		if ((start <= grp_goal) && (grp_goal < end))
			start = grp_goal;
		else
			grp_goal = -1;
	} else {
		if (grp_goal > 0)
			start = grp_goal;
		else
			start = 0;
		end = EXT2_BLOCKS_PER_GROUP(sb);
	}

repeat:
	if (grp_goal < 0) {
		grp_goal = find_next_usable_block(start, bitmap_bh, end);
		if (grp_goal < 0)
			goto fail_access;
		if (!my_rsv) {
			int i;

			for (i = 0; i < 7 && grp_goal > start &&
					!ext2_test_bit(grp_goal - 1,
					     		bitmap_bh->b_data);
			     		i++, grp_goal--)
				;
		}
	}
	start = grp_goal;

	if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal,
			       				bitmap_bh->b_data)) {
		/*
		 * The block was allocated by another thread, or it was
		 * allocated and then freed by another thread
		 */
		start++;
		grp_goal++;
		if (start >= end)
			goto fail_access;
		goto repeat;
	}
	num++;
	grp_goal++;
	while (num < *count && grp_goal < end
		&& !ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group),
					grp_goal, bitmap_bh->b_data)) {
		num++;
		grp_goal++;
	}
	*count = num;
	return grp_goal - num;
fail_access:
	*count = num;
	return -1;
}

/**
 * ext2_try_to_allocate_with_rsv()
 * @sb:     superblock
 * @group:    given allocation block group
 * @bitmap_bh:    bufferhead holds the block bitmap
 * @grp_goal:   given target block within the group
 * @count:    target number of blocks to allocate
 * @my_rsv:   reservation window
 *
 * This is the main function used to allocate a new block and its reservation
 * window.
 *
 * Each time when a new block allocation is need, first try to allocate from
 * its own reservation.  If it does not have a reservation window, instead of
 * looking for a free bit on bitmap first, then look up the reservation list to
 * see if it is inside somebody else's reservation window, we try to allocate a
 * reservation window for it starting from the goal first. Then do the block
 * allocation within the reservation window.
 *
 * This will avoid keeping on searching the reservation list again and
 * again when somebody is looking for a free block (without
 * reservation), and there are lots of free blocks, but they are all
 * being reserved.
 *
 * We use a red-black tree for the per-filesystem reservation list.
 */
static ext2_grpblk_t
ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
      struct buf_head *bitmap_bh, ext2_grpblk_t grp_goal,
      struct ext2_reserve_window_node * my_rsv,
      unsigned long *count)
{
  ext2_fsblk_t group_first_block, group_last_block;
  ext2_grpblk_t ret = 0;
  unsigned long num = *count;

  /*
   * we don't deal with reservation when
   * filesystem is mounted without reservation
   * or the file is not a regular file
   * or last attempt to allocate a block with reservation turned on failed
   */
  if (my_rsv == NULL) {
    return ext2_try_to_allocate(sb, group, bitmap_bh,
            grp_goal, count, NULL);
  }
  /*
   * grp_goal is a group relative block number (if there is a goal)
   * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb)
   * first block is a filesystem wide block number
   * first block is the block number of the first block in this group
   */
  group_first_block = ext2_group_first_block_no(EXT2_SB(sb), group);
  group_last_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);

  /*
   * Basically we will allocate a new block from inode's reservation
   * window.
   *
   * We need to allocate a new reservation window, if:
   * a) inode does not have a reservation window; or
   * b) last attempt to allocate a block from existing reservation
   *    failed; or
   * c) we come here with a goal and with a reservation window
   *
   * We do not need to allocate a new reservation window if we come here
   * at the beginning with a goal and the goal is inside the window, or
   * we don't have a goal but already have a reservation window.
   * then we could go to allocate from the reservation window directly.
   */
  while (1) {
    if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
      !goal_in_my_reservation(&my_rsv->rsv_window,
            grp_goal, group, sb)) {
      if (my_rsv->rsv_goal_size < *count)
        my_rsv->rsv_goal_size = *count;
      ret = alloc_new_reservation(my_rsv, grp_goal, sb,
              group, bitmap_bh);
      if (ret < 0)
        break;      /* failed */

      if (!goal_in_my_reservation(&my_rsv->rsv_window,
              grp_goal, group, sb))
        grp_goal = -1;
    } else if (grp_goal >= 0) {
      int curr = my_rsv->rsv_end -
          (grp_goal + group_first_block) + 1;

      if (curr < *count)
        try_to_extend_reservation(my_rsv, sb,
              *count - curr);
    }

    if ((my_rsv->rsv_start > group_last_block) ||
        (my_rsv->rsv_end < group_first_block)) {
      //rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1);
			printk("invalid rsv window. %s %s\n",__func__,__FILE__);
      BUG();
    }
    ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal,
             &num, &my_rsv->rsv_window);
    if (ret >= 0) {
      my_rsv->rsv_alloc_hit += num;
      *count = num;
      break;        /* succeed */
    }
    num = *count;
  }
  return ret;
}

unsigned long ext2_new_blocks(struct inode *inode,ext2_fsblk_t goal,unsigned long *count)
{
	struct buf_head *bitmap_bh = NULL;
	struct buf_head *gdp_bh;
  int group_no;
  int goal_group;
  ext2_grpblk_t grp_target_blk; /* blockgroup relative goal block */
  ext2_grpblk_t grp_alloc_blk;  /* blockgroup-relative allocated block*/
  ext2_fsblk_t ret_block=0;   /* filesyetem-wide allocated block */
  int bgi;      /* blockgroup iteration index */
  int performed_allocation = 0;
  ext2_grpblk_t free_blocks;  /* number of free blocks in a group */
  struct ext2_group_desc *gdp;
  struct ext2_reserve_window_node *my_rsv = NULL;
  struct ext2_block_alloc_info *block_i;
  unsigned short windowsz = 0;
  unsigned long ngroups;
  unsigned long num = *count; 

	struct super_block *sb = inode->i_sb;
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	struct ext2_super_block *es = sbi->s_es;
	struct ext2_inode_info *ei = inode->i_data;


	if(sb->s_dev == NODEV ||
		 sb->s_roflag ||
		 !sbi || !es || !ei){
		printk("basic checks failed. %s %s\n",
			__func__,__FILE__);
		BUG();
	}

	if(!ei->i_block_alloc_info)
		ext2_init_block_alloc_info(inode);
loop:
	// lock super block
	if(sb->s_flags & LOCK_BITOP){
		sb->s_flags |= WANT_BITOP;
		sleepon(&sb->s_bitop_wait);

		goto loop;
	}

	sb->s_flags |= LOCK_BITOP;

  /*
   * Allocate a block from reservation only when
   * filesystem is mounted with reservation(default,-o reservation), and
   * it's a regular file, and
   * the desired window size is greater than 0 (One could use ioctl
   * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
   * reservation on that particular file)
   */
  block_i = EXT2_I(inode)->i_block_alloc_info;
  if (block_i) {
    windowsz = block_i->rsv_window_node.rsv_goal_size;
    if (windowsz > 0)
      my_rsv = &block_i->rsv_window_node;
  }

  if (!ext2_has_free_blocks(sbi)) {
		printk("disk full. not free blocks for allocation. %s %s\n",
			__func__,__FILE__);
		BUG();
  }

  /*
   * First, test whether the goal block is free.
   */
  if (goal < le32_to_cpu(es->s_first_data_block) ||
      goal >= le32_to_cpu(es->s_blocks_count))
    goal = le32_to_cpu(es->s_first_data_block);
  group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
      EXT2_BLOCKS_PER_GROUP(sb);
  goal_group = group_no;
retry_alloc:
  gdp = ext2_get_group_desc(EXT2_SB(sb), group_no, &gdp_bh);
  if (!gdp){
		printk("failed to get ext2 group descriptor. %s %s\n",
			__func__,__FILE__);
		BUG();
	}

  free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);

  /*
   * if there is not enough free blocks to make a new resevation
   * turn off reservation for this allocation
   */
  if (my_rsv && (free_blocks < windowsz)
    && (free_blocks > 0)
    && (rsv_is_empty(&my_rsv->rsv_window)))
    my_rsv = NULL;

  if (free_blocks > 0) {
    grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
        EXT2_BLOCKS_PER_GROUP(sb));
    bitmap_bh = read_block_bitmap(sb, group_no);
    if (!bitmap_bh){
			printk("failed to read block bitmap. %s %s\n",
				__func__,__FILE__);
			BUG();
		}

    grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
          bitmap_bh, grp_target_blk,
          my_rsv, &num);
    if (grp_alloc_blk >= 0)
      goto allocated;
  }

  ngroups = EXT2_SB(sb)->s_groups_count;
  barrier();

  /*
   * Now search the rest of the groups.  We assume that
   * group_no and gdp correctly point to the last group visited.
   */
  for (bgi = 0; bgi < ngroups; bgi++) {
    group_no++;
    if (group_no >= ngroups)
      group_no = 0;
    gdp = ext2_get_group_desc(EXT2_SB(sb), group_no, &gdp_bh);
    if (!gdp){
			printk("failed to get group descriptor. %s %s\n",
				__func__,__FILE__);
			BUG();
		}

    free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
    /*    
     * skip this group if the number of
     * free blocks is less than half of the reservation
     * window size.
     */
    if (my_rsv && (free_blocks <= (windowsz/2)))
      continue;

    brelse(bitmap_bh);

	  bitmap_bh = read_block_bitmap(sb, group_no);
    if (!bitmap_bh){
			printk("failed to get bitmap for block group. %s %s\n",
				__func__,__FILE__);
			BUG();
		}
    /*
     * try to allocate block(s) from this group, without a goal(-1).
     */
    grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
          bitmap_bh, -1, my_rsv, &num);
    if (grp_alloc_blk >= 0)
      goto allocated;
  }

  /*
   * We may end up a bogus ealier ENOSPC error due to
   * filesystem is "full" of reservations, but
   * there maybe indeed free blocks avaliable on disk
   * In this case, we just forget about the reservations
   * just do block allocation as without reservations.
   */
  if (my_rsv) {
    my_rsv = NULL;
    windowsz = 0;
    group_no = goal_group;
    goto retry_alloc;
  }
  /* No space left on the device */
	printk("no space left on the device. %s %s\n",
		__func__,__FILE__);
	BUG();

allocated:

  //ext2_debug("using block group %d(%d)\n",
  //    group_no, gdp->bg_free_blocks_count);

  ret_block = grp_alloc_blk + ext2_group_first_block_no(EXT2_SB(sb), group_no);

  if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
      in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
      in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
          EXT2_SB(sb)->s_itb_per_group) ||
      in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
          EXT2_SB(sb)->s_itb_per_group)) {
    printk("ext2_new_blocks",
          "Allocating block in system zone - "
          "blocks from %u, length %lu",
          ret_block, num);
    /*
     * ext2_try_to_allocate marked the blocks we allocated as in
     * use.  So we may want to selectively mark some of the blocks
     * as free
     */
    goto retry_alloc;
  }

  performed_allocation = 1;

  if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
    printk( "ext2_new_blocks",
          "block(%u) >= blocks count(%d) - "
          "block_group = %d, es == %p ", ret_block,
      le32_to_cpu(es->s_blocks_count), group_no, es);
		printk("can not allocate any more. %s %s\n",
			__func__,__FILE__);
		BUG();
  }

  group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
  sbi->s_freeblocks_counter -= num;

	bitmap_bh->b_flags |= B_DIRTY;
  brelse(bitmap_bh);
	*count = num;
	
	// unlock super block
	sb->s_flags &= ~(LOCK_BITOP);
	if(sb->s_flags & WANT_BITOP){
		sb->s_flags &= ~WANT_BITOP;
		wakeup(&sb->s_bitop_wait);
	}

	return ret_block;
}

/**   
 * ext2_discard_reservation()
 * @inode:    inode
 *      
 * Discard(free) block reservation window on last file close, or truncate
 * or at last iput().
 *    
 * It is being called in three cases:
 *  ext2_release_file(): last writer closes the file
 *  ext2_clear_inode(): last iput(), when nobody links to this file.
 *  ext2_truncate(): when the block indirect map is about to change.
 */
void ext2_discard_reservation(struct inode *inode)
{ 
  struct ext2_inode_info *ei = EXT2_I(inode);
  struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
  struct ext2_reserve_window_node *rsv;
  
  if (!block_i)
    return;

  rsv = &block_i->rsv_window_node;
  if (!rsv_is_empty(&rsv->rsv_window)) {
    if (!rsv_is_empty(&rsv->rsv_window))
      rsv_window_remove(inode->i_sb, rsv);
  }
}

void ext2_free_blocks(struct inode *inode,unsigned long block,unsigned count)
{
  struct buf_head *bitmap_bh = NULL;
  struct buf_head * bh2;
  unsigned long block_group;
  unsigned long bit;
  unsigned long i;
  unsigned long overflow;
  struct ext2_group_desc * desc;
  unsigned freed = 0, group_freed;
	struct super_block *sb = inode->i_sb;
	struct ext2_sb_info *sbi = sb->s_data;
	struct ext2_super_block *es = sbi->s_es;

	if(sb->s_dev == NODEV ||
	   sb->s_roflag ||
		!sbi || !es){
		printk("invalid super block. %s %s\n",__func__,__FILE__);
		BUG();
	}

loop:
	// lock super block
	if(sb->s_flags & LOCK_BITOP){
		sb->s_flags |= WANT_BITOP;
		sleepon(&sb->s_bitop_wait);

		goto loop;
	}
	sb->s_flags |= LOCK_BITOP;

  if (block < le32_to_cpu(es->s_first_data_block) ||
      block + count < block ||
      block + count > le32_to_cpu(es->s_blocks_count)) {
    printk("ext2_free_blocks",
          "Freeing blocks not in datazone - "
          "block = %lu, count = %lu", block, count);
		printk("failed to free blocks. %s %s\n",
			__func__,__FILE__);
		BUG();
  }

do_more:
  overflow = 0;
  block_group = (block - le32_to_cpu(es->s_first_data_block)) /
          EXT2_BLOCKS_PER_GROUP(sb);
  bit = (block - le32_to_cpu(es->s_first_data_block)) %
          EXT2_BLOCKS_PER_GROUP(sb);
  /*
   * Check to see if we are freeing blocks across a group
   * boundary.
   */
  if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
    overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
    count -= overflow;
  }
  bitmap_bh = read_block_bitmap(sb, block_group);
  if (!bitmap_bh){
		printk("failed to get block bitmap. %s %s\n",
			__func__,__FILE__);
		BUG();
	}

  desc = ext2_get_group_desc (EXT2_SB(sb), block_group, &bh2);
  if (!desc){
		printk("failed to get block descriptor. %s %s\n",
			__func__,__FILE__);
		BUG();
	}

  if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
      in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
      in_range (block, le32_to_cpu(desc->bg_inode_table),
          sbi->s_itb_per_group) ||
      in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
          sbi->s_itb_per_group)) {
    printk("ext2_free_blocks",
          "Freeing blocks in system zones - "
          "Block = %lu, count = %lu",
          block, count);
		printk("range test failed. %s %s\n",__func__,__FILE__);
		BUG();
  }

  for (i = 0, group_freed = 0; i < count; i++) {
    if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
            bit + i, bitmap_bh->b_data)) {
      printk("bit already cleared for block %lu", block + i);
			printk("block already freed? %s %s\n",
				__func__,__FILE__);
			BUG();
    } else {
      group_freed++;
    }
  }

	bitmap_bh->b_flags |= B_DIRTY;
  brelse(bitmap_bh);

  group_adjust_blocks(sb, block_group, desc, bh2, group_freed);
  freed += group_freed;

  if (overflow) {
    block += count;
    count = overflow;
    goto do_more;
  }

	// unlock super block
	sb->s_flags &= ~(LOCK_BITOP);
	if(sb->s_flags & WANT_BITOP){
		sb->s_flags &= ~WANT_BITOP;
		wakeup(&sb->s_bitop_wait);
	}

}
